SELECT 
  discussion_posts.*, 
  discussion_messages.message, 
  discussion_rating.rating_value 
FROM 
  discussion_posts 
  LEFT JOIN discussion_messages ON discussion_messages.post_id = discussion_posts.post_id 
  LEFT JOIN discussion_rating ON discussion_rating.post_id = discussion_posts.post_id 
WHERE 
  discussion_posts.thread_id = 4709 
  AND discussion_posts.status = 'A' 
ORDER BY 
  discussion_posts.timestamp DESC 
LIMIT 
  0, 10

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "9.46"
    },
    "ordering_operation": {
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "discussion_posts",
            "access_type": "ref",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "key": "thread_id",
            "used_key_parts": [
              "thread_id"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 22,
            "rows_produced_per_join": 2,
            "filtered": "10.00",
            "cost_info": {
              "read_cost": "5.50",
              "eval_cost": "0.22",
              "prefix_cost": "7.70",
              "data_read_per_join": "985"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "name",
              "timestamp",
              "user_id",
              "ip_address",
              "status"
            ],
            "attached_condition": "(`goimagine`.`discussion_posts`.`status` = 'A')"
          }
        },
        {
          "table": {
            "table_name": "discussion_messages",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
            ],
            "key_length": "3",
            "ref": [
              "goimagine.discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.77",
              "eval_cost": "0.22",
              "prefix_cost": "8.69",
              "data_read_per_join": "52"
            },
            "used_columns": [
              "message",
              "post_id"
            ]
          }
        },
        {
          "table": {
            "table_name": "discussion_rating",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
            ],
            "key_length": "3",
            "ref": [
              "goimagine.discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.55",
              "eval_cost": "0.22",
              "prefix_cost": "9.46",
              "data_read_per_join": "35"
            },
            "used_columns": [
              "rating_value",
              "post_id"
            ]
          }
        }
      ]
    }
  }
}

Result

post_id thread_id name timestamp user_id ip_address status message rating_value
1540 4709 Barbara Allison 1653584666 9380 44ccee7d A What's not to like from this seller! Items are always better than described. Very creative. She's super helpful; prompt communication & shipping; and always carefully wrapped. 5
1497 4709 ESTHER JIM 1652714064 5592 4845ae5a A The seller is very helpful and friendly,love her shop,we'll come back soon. Love the beautiful cover minders.thanks again. 5
1458 4709 Barbara Allison 1651963449 9380 44ccee7d A As I've said several times before...this seller's a "winner." Can't go wrong with her creativeness. Unique. Excellent communication & always helpful. Prompt shipping & carefully packaged 5
1384 4709 Barbara Allison 1650659899 9380 44ccee7d A Can't go wrong with this seller. Items always better than described/pictured. Creative & meticulously made. Promptly shipped & carefully wrapped. She's a "winner!" 5
1328 4709 Barbara Allison 1649450131 9380 44ccee7d A Running out of complements for this seller. Love everything I've bought. You can't go wrong with her. Helpful, prompt communication, pictures don't do the items justice. 5
1327 4709 Barbara Allison 1649449973 9380 44ccee7d A This seller is an absolute "winner." Everything purchased is always top notch. Better than pictured/described. Prompt shipping & carefully packaged. Extremely helpful. 5
1282 4709 Barbara Allison 1647900384 9380 44ccee7d A Items are even better than pictured/described. Can't go wrong w/ this seller. Always promptly shipped & very carefully wrapped. She's a "winner." 5
1249 4709 Barbara Allison 1647119273 9380 44ccee7d A Have said several times before...this seller's a "winner." No matter the item, they are always better than described/pictured. Talented; Unique; Creative!!! Prompt shipping; carefully wrapped. Can't go wrong with her! She's definitely a keeper. 5
1223 4709 ESTHER JIM 1645967869 5592 4845ae5a A Again,very happy with my purchase,fast shipping and items well packed,Lisa is a great seller,always willing to help,a shop with beautiful fridge magnets,i'll definitely will buy more soon. Esther 5
1221 4709 Barbara Allison 1645788487 9380 44ccee7d A Candy magnets hilarious. Didn't realize arms/legs move. Sparkly/perfect. Even better than pictured/described. I've said it before, but will say it again...seller's always promptly communicative & extremely helpful. Mark her a "favorite!" 5